1. Field of the Invention
The present invention relates to a spinning reel having a balancing means for restricting rotational imbalance of a rotor.
2. Description of the Related Art
There is known a spinning reel having a balancer weight attached to a rotor as the above-mentioned balancing means (e.g. Japanese laid-open utility model gazette No. 52-80887).
However, with the above described balancer weight it is difficult to achieve complete solution to the rotational imbalance. On the other hand, has been practically impossible to modify a configuration of the rotor or an arrangement of components thereof for the sole purpose of improvement in the balance.
With this type of balancer, the farther the balancer is disposed relative to the rotational axis, the greater a value of the moment becomes. Therefore, in often times, a balancer of a relatively small weight will suffice for the purpose. However, in the case of the conventional construction where the balancer is attached to a cylindrical portion of the rotor, since this cylindrical portion is usually arranged at an inner side of a skirt portion of the rotor, the balancer cannot project outwards at this portion, so that the balancer necessarily tends to be large in weight.
Then, in order to arrange the balancer without being interfered with by the skirt portion of the spool, it is conceivable to arrange the balancer at a rear end portion (on the side of the spool body) of the rotor. However, since this portion usually is not formed with high manufacturing precision there arises a new problem that the arrangement of the balancer at this position may adversely affect the physical strength of this portion.
Moreover, in disposing the balancer at the rear end portion of the rotor, if the baler is attached here in such a manner as to project significantly from an outer periphery of the rotor, this balancer may come into contact with e.g. an angler""s finger in the course of rotation of the rotor.
Accordingly, a primary object of the present invention is to provide an improved spinning reel of the above type which allows a user of the reel to restrict rotational vibration of the rotor within a permissible range thus allowing smooth line-retrieving operation by well balancing the rotor rotation without sacrificing other functions of the spinning reel.
For a accomplishing the above-noted object, according to the characterizing features of the present invention, a spinning reel comprises:
a reel body;
a rotor attached to the reel body and rotatable about a longitudinal axis for retrieving a fishing line; and
a balancing means attached to the rotor for restricting an imbalance amount of rotation of the rotor substantially within 200 g -mm.
Functions and effect of the above features will be described next.
By using a commercially available rotational balance testing machine the present inventor has conducted intensive experiments with a plurality of spinning reels having rotor diameters ranging approximately between 40 mm and 100 mm. Then, it has been found out that a rotational imbalance amount not exceeding approximately 200 g -mm is sufficient to restrict vibration resulting from the imbalance to such a degree as not to provide discomfort to the user while complete elimination of rotational vibration is yet to be achieved with said amount.
Therefore, the construction of the present invention can achieve practically sufficient performance with the advantage of facility in designing of the rotor in comparison with the conventional construction which involves a great amount of works  work in designing often with the aid of a computer to determine the appropriate disposing position and the weight of the balancing means.
That is, as described above, through the experiments, the present inventor has come to realize that a rotational imbalance amount not exceeding approximately 200 g -mm is sufficient to restrict vibration resulting from the imbalance to such a degree as not to provide discomfort to the user while complete elimination of rotational vibration is yet to be achieved with said amount.
Then, the inventor proceeded to obtain an amount of deviation in the center of gravity as a value derived by dividing the rotational imbalance amount by a  the mass of the rotor. Then, it was found that this deviation amount is maintained substantially lower than 3.5 mm in the above-described situation.
Therefore, by restricting the gravity-center deviation amount substantially within 3.5 mm, it is possible to determine a reference value which is independent of the size of the rotor, whereby a more precise rotor balance control becomes possible.
According to a further embodiment of the invention, a spinning reel comprises:
a reel body;
a rotor attached to the reel body and rotatable for retrieving a fishing line, the rotor including a base end portion supported to the rotor to be rotatable about a longitudinal axis and a pair of arm portions extending from the base end portion along the longitudinal axis;
a bail extending between the arm portions;
the rotor and the bail together constituting a rotary unit having two predetermined positions spaced apart from each other with a predetermined distance therebetween along the longitudinal axis; and
a balancing means attached to the rotor for restricting an imbalance amount of rotation of the rotor substantially within 200 g -mm at each of the two reference positions.
The above features can achieve the distinguished functions and effects to be described next.
Based on the results of the afore-described experiments by restricting the imbalance amount rotation lower than approximately 200 g -mm at each reference position it becomes possible to reduce a centrifugal force at the rotor face rotating about the longitudinal axis at the respective reference positions thereby to achieve a static balance and also to restrict generation of torque about an axis normal to the longitudinal axis thereby to achieve a dynamic balance.
In short, through the simple arrangement for restricting the rotational imbalance amount within 200 g -mm, in the case also of a rotor having the base end portion and the arm portion disposed side by side along the longitudinal axis, it has become possible to achieve not only the static balance but also the dynamic balance through the restriction of the torque generation, such that the spinning reel having these features can provide a smooth line retrieving operation without giving the user uncomfortable feel.
Further, and other objects, features and effects of the invention will become more apparent from the following more detailed description of the embodiments of the invention with reference to the accompanying drawings.